Thanks for your help.
I managed to get the leaver to move and it moved back automatically when I turned the heating on but it doesn't seem to have sorted the problem.
So, I'm thinking that the valve might be stuck open inside.
Is this likely and how would I solve this without dismantling...
I have recently encountered a strange issue.
A home that I visited has a Worcester Greenstar Boiler installed. The owner was saying that even though they have now turned their central heating on and only have the water on 1st thing they have noticed that certain radiators still get warm...